IntroductionIn countries with a rich history, such as Europe, the historical
research is useful to a number of different scientists, among which are
seismologists. For Greece, especially, which is known to have suffered the
destructive effects of earthquakes since antiquity, the detailed knowledge
of historical earthquakes is useful for seismic hazard assessment which will
lead to the reduction of seismic risk and the mitigation of damage and human
losses from future earthquakes.The present study is part of a joint effort of the European
countries towards the thorough historical investigation of pre-instrumental
earthquakes. The first part is concentrated in historical research carried
out in order to assess the results of such earthquakes in relation to buildings
and people.The historical research is mainly directed towards the collection
of information on the studied subject. Often, the available information is
poor, and therefore the historian must look at the historical archives in
order to enrich his data set. The new information, published or unpublished,
is translated, when needed, to the contemporary language and its contents
are added to the already existing archives. Then, in collaboration with
seismologists and relevant scientists, the seismological information is assessed
and evaluated.The Ionian islands were chosen for study for different reasons,
the most important of which is their location at the western borders of Greece,
and near the Italian territory. The domination of the Venetians in the 18th
century, the state of which was perfectly organized, implies that information
can also be located in the archives of this state. Additionally, the inhabitants
kept their own historical records and thus the set of information is expected
to be richer.The Ionian islands suffered and are still suffering from destructive
earthquakes, which have become a part of the life of the inhabitants. The
Cefalonia 1767 and Leukada 1769 earthquakes are known to have caused major
damage in all the islands, and they point to a good example for further
research.This historical research was directed towards any information
relative to the Ionian islands in the 18th century and the results of the
information collected are presented in the process of the present
study.

Political, administrative, social and economic aspects of Greece in the
18th century

Political and administrative situationIn the 18th century the mainland and the Aegean islands were
occupied by the Ottoman empire which had installed rulers in all the major
cities of Greece. These rulers had full political and economic authority,
thus affording no freedom to the inhabitants.The Ionian area of Western Greece includes the islands of Corfu,
Paxoi, Leukada, Ithaci, Cefalonia, Zante, Stromfadi and Cythera (Fig. 1).
During the 18th century this area was under the domination of the Venetian
state. This domination was imposed gradually on the islands. More specifically,
Corfu and Paxoi were occupied in 1360, Cythera in 1363, Zante and Stromfadi
in 1479-1485, Cefalonia and Ithaca in 1500, Leukada in 1684. In 1797, following
the fall of the Venetian state, the islands passed under French
occupation.The situation in the area can be summarized in the following
features. Venice practised absolute power through the Provveditore Generale
da Mar, who resided in Corfu. Additionally, in every island there was
a Venetian ruler (Provveditore Ordinario), who remained in this position
for a certain time period (usually for two years, Tab. 1). The top administrative
posts in all the islands were taken up by Venetian officials, or locals of
noble birth. The election of the latter was performed always with the approval
of the central authorities.The dispute which existed to a lesser degree in the previous
centuries between the nobles (nobili) and the middle class
(cittadini) was intensified during that period. Sensitive to their
class conscience, the middle class demanded and eventually managed to be
included in the Board of Nobles.

Fig. 1 - The territory of Central Greece and the Ionian Islands
under the Venetian occupation (18th century).

Tab. 1 - The Venetian administrative system in Leukada during
the 17th and 18th centuries.

However, at the same time, the friction between the middle class
and the peasants often resulted in popular uprisings. Most of the time the
reason was the miserable living conditions of the peasants, who often suffered
abuse by government officials, and had to bear heavy direct and indirect
taxation. During the studied period several countries, especially European,
interested in the political stability of Eastern Europe, placed embassies
and consulates in the major cities of Greece. Amongst them were England,
Russia, Denmark, America, Ragusa, etc. Venice, in its turn, had placed 30
consulates and subconsulates in Greece and the countries of Eastern
Mediterranean.

Social and economic situationIn spite of the aforementioned unfavourable circumstances, the
islands in the 18th century are characterized by a remarkable economic bloom,
related to the general political changes in Europe, with direct impact on
the Western Mediterranean. Thus, in spite of the limitations and the
interventions of the Venetians, trade and shipping was developed and productivity
was increased, as a result of taking advantage of the fertile soils of the
islands and the customary handicraft of the locals (e.g. salt-pans and hatcheries
in Leukada, bread production in Cefalonia, etc.).The Venetians were interested in the increase of the population
of the islands, and in some cases (e.g. Leukada) brought additional inhabitants
from the mainland. As a result, the population of the islands increased slowly
but steadily (Tab. 2). Some negative factors, which did not allow a more
rapid increase and, consequently, a more general development, were piracy
(which had increased dangerously), epidemics (which were a real curse in
many cases) and finally earthquakes, which often caused major damage and
loss of human life. At the same time the mainland suffered the Turkish yoke. The
Turks did not allow any administrative rights to the Greeks, imposed unbearable
taxes on the farmers, and the economic conditions of the inhabitants were
very poor. Such conditions contributed to the Greek revolution of 1821. For
all these reasons the population of the mainland (Tab. 2) fell
dramatically.In the Ionian islands the inhabitants also developed their own
local art. Many of the islanders were well educated and built the well known
library of Zante. The structures on the islands were mainly old, stone built,
with thick walls and small openings. The architecture was influenced by the
regular earthquakes, but the real anti-seismic structures were only the public
buildings and churches. The majority of the people were too poor to afford
basic luxuries, or even to properly restore their houses which were damaged
by earthquakes. Also, due to their strong religious beliefs, they were more
interested in the restoration of their churches, and for this they often
required financial aid from the Venetians.The history of Greece in antiquity and byzantine times attracted
many adventurous travellers from the countries of Europe and also from the
Americas. Many of them were only interested in the antiquities of Greece,
which they later sold at remarkable prices in their countries. Most travellers
were British and French, and the rest came from countries of Western Europe.
The Ionian islands, due to their position near Europe and their political
freedom to some degree, were visited more often than the mainland.

Ionian Islands

Corfu

22,170 (1602)

27,056 (1616)

20,000 (1675)

44,333 (1766)

Cefalonia

50,000 (1630)

70,000 (1660)

47,000 (1715)

21,659 (1766)

Zante

28,492 (1670)

25,000 (1675)

25,325 (1766)

30,000 (1770)

Leukada

9,000 (1684)

12,000 (1760)

11,760 (1766)

15,000 (1778)

Cythera

6,000 (1760)

6,183 (1766)

8,000 (1787)

Ithaki

2,500 (1622)

2,500 (1760)

Greek Mainland

Patras

10,000 (1765)

30,000 (1767)

Mistras

ca. 15-18,000 (1799)

Tripolitsa

ca.15-20,000

Nauplion

ca. 7-10,000

Methon

ca. 4,000

Coroni

ca.1,500

Navarino (Pilos)

ca. 1,000

Vostitsa (Aiyio)

2,000 (1765)

4,000 (1799)

Arkadia (Kiparissia)

ca. 5,000

Kalamata

ca. 2,500

Korinthos

ca. 5,000

Athens

10,000 (1788)

Tab. 2 - Population of the Ionian islands and major cities
of the Greek mainland

in the 17th and 18th centuries.

Historical research on earthquakesFor the study of historical earthquakes all the relevant information
concerning the period investigated is gathered. The present study is mainly
directed towards the search for published or unpublished sources referring
to the Cefalonia 1767 and Leukada 1769 earthquakes, or to other earthquakes
of the same period. In addition, all other monographs, published papers,
books, etc. referring to the political, administrative, social and economic
situation of the period, were searched for a better knowledge of the situation
of the suffering areas. The geologic and seismotectonic features of the area
are also important, since they are a useful tool for the calibration of the
results.In the process of the study different kinds of sources were
collected. Each one was attributed to a source list, according to its contents,
and the information the sources contained was evaluated both partly and as
a whole. As a consequence, all the references are listed in the different
types of sources.

CataloguesThe catalogues of earthquakes usually refer to a certain time
period and a specific area. The catalogues of historical earthquakes contain
information on events before 1900, i.e. the pre-instrumental earthquakes.
The information is derived from descriptions of reporters of the time, references
in newspapers, monographs, monastery notes, etc. The catalogues are distinguished
into classical compilations (references, section 1) and modern catalogues
(references, section 2). In modern catalogues the focal parameters of the earthquakes
are derived from collection and evaluation of all the available macroseismic
information, which is often calibrated using the 20th century instrumental
catalogues.

CompilationsIn this section two categories of sources are listed. The former
is the methodological published sources (references, section 3), concerning
archive guides, sources inventories, geological and geophysical studies,
etc. Apart from the published sources of information of general character,
more detailed ones were devoted exclusively to the studied earthquakes. Their
importance is based on the following fact: their authors derive their information
from unpublished archive material of the period in which these earthquakes
occured. This is why their witness reports are so relevant and
consistent.The second category is specific sources and concerns the direct
original unpublished sources. In the case of earthquakes which occured in
the Ionian Sea during the 18th century, as well as of the history of the
islands during this period, ample archive material has been saved, most of
which was unknown. Expecially for the two studied earthquakes four unpublished
sources were found (Tab. 3). For further research in this material and in
particular for the earthquakes of 1767 and 1769, the existing local archives
of the Ionian islands as well as churches, monasteries and private archive
collections contain such information.

Sources for the 1767 earthquake

1. LetterSender: The villagers of ComilioRecipient: Provveditore estraordinario di Santa Maura(Lorenzo Moro)Date: September 22, 1767Abstract: A major earthquake occurred at 2 hours before noon.
Comilio was completely destroyed. All the houses collapsed, most of them
from their foundations. The churches were destroyed. Panic spread amongst
the inhabitants.From: Historical Archive of Leukada, Reggimento Lorenzo Moro,
f. 3, no. 381

2. LetterSender: The villagers of AthaniRecipient: Provveditore Estraordinario di Santa Maura(Lorenzo Moro)Date: September 22, 1767Abstract: A major earthquake occurred at sunrise. Almost
all the houses in Athani were destroyed. All the churches were also destroyed,
and we were therefore not able to follow the service. We kindly request the
hasty restoration of damage.From: Historical Archive of Leukada, Reggimento Lorenzo Moro,
f. 3, no. 382

3. LetterSender: The villagers of Ayios PetrosRecipient: Provveditore Estraordinario di Santa Maura(Lorenzo Moro)Date: [September 22, 1767)Abstract: On September 22 a major earthquake occurred. In
Ayios Petros all the churches and houses collapsed. Two people were seriously
injured. The wine barrels fell over and our wine crop was destroyed. We kindly
request you to restore the damages as soon as possible.From: Historical Archive of Leukada, Reggimento Lorenzo Moro,
f. 3, no. 383

4. LetterSender: Elderly inhabitants of DraganoRecipient: Provveditore Estraordinario di Santa Maura(Lorenzo Moro)Date: [September 22, 1767]Abstract: All the houses of the village collapsed from their
foundations because of the earthquake. The grain crops and wine barrels were
destroyed and buried under the ruins. We kindly request you to quickly restore
the damage.From: Historical Archive of Leukada, Reggimento Lorenzo Moro,
f. 3, no. 384.

Tab. 3 - Specific unpublished historical sources.

The 1767 Cefalonia and 1769 Leukada earthquakes

SourcesThis section contains all the available information about the
18th century earthquakes of Cefalonia and Leukada. The information contained
in the modern catalogues was poor, due to the fact that it was limited in
the meizoseismal area. Thus, for the 1767 Cefalonia earthquake the research
was directed towards the original sources. As far as the 1769 Leukada earthquake
is concerned, the information was more systematic, because, not only has
this event been studied in the XIX century, but also the required sources
have already been confined.Besides, there is very little information about this earthquake
from the area of Western Greece, where they were expected to be felt with
rather high intensities. The available archives of that period are very few
(most of them were transferred to Ankara and Constantinople, or were destroyed).
Thus the available information is limited to few reports: both earthquakes
were felt in the towns of Naupaktos and Rion, whereas the Cefalonia 1767
earthquake was felt in Meteora (Ambraseys, personal communication).The whole set of sources was completed with those of the Venice
State Archives provided by the Italian researchers (Daltri e Albini, 1991),
which have already been systematically studied. From these sources it made
clear the excellent administrative structure of this state in the 18th century.
After an earthquake a whole bureaucracy was initiated, beginning from the
locals who asked for financial aid for the restoration of their houses and
churches, and, through the Provveditore Generale da Mar, leading to the Venetian
Senate, which was the final authority to decide if this request would be
satisfied (Tab. 4).For a better use in the future of this set of information, and
in order to obtain a systematic data bank, the contents of the sources concerning
earthquakes were computerized.

Research problemsFrom the research made, certain problems arose, which are listed
below:a) In the case of Zakinthos the information to hand is limited
due to the fact that the rich archive material of the island was destroyed
during the earthquake of 1953. The existing historical archives of the island
contain material of the 19th and 20th centuries, but hardly anything on the
18th century. This important absense of material is somewhat alleviated by
the rich bibliography up to 1953. Specifically, numerous written studies
utilized archive material (references, section 3), which was later destroyed.
In this way the knowledge on this subject is more or less completed.b) The second serious problem concerns the part of Western Greece
facing the Ionian islands, where the studied earthquakes might have been
felt. The relevant archive material on this area is insufficient. This
aforementioned serious lack of material can be substituted up to now by the
archive material saved by monasteries of the area, which involves documents,
books of the time, notes and short chronicles.

ConclusionsThe historical research concerning earthquakes is not a limited
task. Together with the required information, relevant interesting material
can be revealed, which was unknown up to date.

The detailed study of the two Ionian historical earthquakes
of 1767 and 1769 provided an almost complete information set of wide subjects,
which is of interest not only to the historian and the seismologist, but
also to the civil engineer, the architect and the town planner.The importance of this study is evident after the seismological
interpretation has been carried out, and the effects of the earthquakes have
been assessed in terms of macroseismic information. Such studies are therefore
indispensable for all the historical earthquakes, especially for countries
with high seismicity, such as Greece.The problems that arise are not negligible, but the experience
derived can be very helpful for the future research of other earthquakes
of the same or other historical periods. The already existing derivatives
will make the research easier and therefore the present study can act as
a pilot study towards this aim. The future researcher can profit from this
experience, direct his research with the aim of avoiding the existing problems,
and thus his study will not start from zero.There is another important aspect of such studies. The historical
research at home and abroad is an initiative for researchers from different
countries to collaborate and present common results.

AcknowlegdementsThe authors wish to thank our Italian colleagues, especially
Dr. M. Stucchi and Dr. P. Albini for providing the Venice State archive material
concerning the two earthquakes, which has already been published and therefore
was not included as references in the present study, and for their fruitful
discussions.